The present invention relates to an accumulator to modulate line pressure within a control system for a hydraulically operated mechanism, such as a frictional engagement mechanism of an automatic transmission for an automobile.
In a conventional hydraulic transmission for an automobile, it has been observed that when the line pressure is rapidly applied to the frictional engagement mechanism to change the drive power train of the transmission, the mechanism is suddenly connected to engine torque to cause undesired and unpleasant shocks. On the other hand, if the line pressure increases slowly, slips occur within the frictional engagement mechanism to give unpleasant feeling or sensitive and to cause over-running of the engine. To eliminate such drawbacks, it is required that engagement and disengagement of the mechanism is properly conducted in accordance with changes of the engine torque by shifting of the drive power train in the transmission.